The invention relates to an arrangement and a method for generating a fault signal in a motor vehicle.
A signal is needed for various functions in the engine control (for example, idle control, ignition angle intervention in response to an opening of the clutch) and/or for a road speed control or a distance control. In a motor vehicle, this signal is needed to indicate the state of the clutch (open/closed). To determine the operating state of the clutch, a switch contact can be mounted, for example, directly on the clutch pedal actuated by the driver. The position of such a switch then detects whether the clutch pedal and therefore the clutch is activated or not. For this purpose, the switch is connected via a cable to corresponding control apparatus (for example, engine control apparatus, distance control apparatus).
The functions in the corresponding control apparatus would not run optimally or not at all when there is a defect on such a clutch switch or when there is a break in the cable or when the cable drops off. In this way, fault reactions can occur for the functions which evaluate the position of the clutch switch.
The object of the present invention is to reliably monitor the function of the clutch switch without additional hardware complexity.
The invention proceeds from a motor vehicle having a clutch, which is mounted in the drive train of the motor vehicle, and a transmission which is mounted in the drive train and is changeable with respect to its transmission ratio. Furthermore, means are provided which generate a clutch signal which represents the actuation of the clutch.
The essence of the invention is that a change of the transmission ratio is detected. According to the invention, monitoring means are provided by means of which a fault signal is generated in dependence upon the detected change and the generated clutch signal. The fault signal then indicates whether the means, which generates the clutch signal, operates properly.
The function of the clutch switch can be effectively diagnosed by the generation of the fault signal in accordance with the invention. Especially an entry into a fault memory is undertaken in response to a detected defect.
In this way, a rapid and reliable determination can be made as to why specific functions in the corresponding control apparatus are not optimally run through or are not run through at all.
With the diagnosis of the invention, customer service or the application personnel (during the development phase of the individual control apparatus) can rapidly determine with the aid of the fault memory why, for example, the vehicle engine has a higher fuel consumption or why the road speed control and/or the distance control can no longer be activated.
It is especially advantageous when the change of the generated clutch signal, which is detected in response to the change of the transmission ratio, is evaluated for generating the fault signal. Here, it is especially provided that the fault signal is generated when, in response to a pregiven number of changes of the transmission ratio:
no change of the generated clutch signal is detected; or,
only a pregiven lower number of changes of the generated clutch signal are detected than the pregivable number of changes of the transmission ratio.
In an advantageous embodiment of the invention, it is provided that the presence of a pregiven first operating range of the motor vehicle is detected and the fault signal is further generated in dependence upon the detected first operating range. Here, it is especially provided that the first operating range is pregiven in that, in this first operating range, no change of the transmission ratio is possible without an actuation of the clutch. To generate a fault signal, only the changes of the transmission ratio are applied which take place during the presence of the first operating range.
The essence of this configuration is that a check is made as to whether in the operating range in which the gear change takes place, also each gear change must be connected to an actuation of the clutch. This increases the reliability of the diagnosis according to the invention.
Rpm quantities can be detected to detect the presence of the pregivable first operating range. The rpm quantities represent the output rpm of the motor vehicle engine and an rpm present at the transmission. The presence of the first operating range is then detected in dependence upon the detected rpm quantities.
In a further embodiment of the invention, it is provided that the monitoring means is so configured that the presence of a pregivable second operating region of the motor vehicle is detected and the fault signal is further generated in dependence upon the detected second operating region. Here, it is especially provided that an accelerator pedal value and/or a speed value and/or an engine rpm value is detected. The accelerator pedal value represents the position of the accelerator pedal actuated by the driver of the motor vehicle and the speed value represents the vehicle longitudinal speed and the engine rpm value represents the output rpm of the vehicle engine. The second operating region is then pregiven in that in this second operating region:
the detected accelerator pedal value is greater than a first threshold value; and/or,
the detected speed value is greater than a second threshold value; and/or,
the detected engine rpm value is greater than a third threshold value; and/or,
the time-dependent change of the detected engine rpm value is less than a fourth threshold value.
To generate the fault signal, only the changes of the transmission ratio are applied which take place during the presence of the second operating region.
With this embodiment of the invention, it is advantageously ensured that the vehicle engine is operated during the transmission shifting operation sufficiently long in an operating range in which the gear detection can operate reliably. Especially, it is intended, inter alia, that driving over a poor stretch of roadway, drive train vibrations and slipping tires are detected which put into question a reliable gear detection and therefore a reliable diagnosis of the clutch switch.
The essence of a further variation of the invention is that the diagnosis of the clutch switch takes place at a start of the vehicle engine. Here, a start of the vehicle engine is first detected. The fault signal is then generated in dependence upon the detected engine start, the presence of the clutch signal and the detected roadspeed.
Here, it is especially provided that, for generating the fault signal, the change of the generated clutch signal is evaluated. This clutch signal is in response to a change of the detected speed value detected after the engine start.
To exclude a towing of the vehicle from the diagnosis, it can be provided that the fault signal is only generated when the speed value, which is detected at the detected engine start, is essentially zero.